Window coverings, such as venetian blinds, roman shades, cellular shades or pleated shades, often have a headrail, a bottom rail and window covering material between the headrail and the bottom rail. U.S. Pat. Nos. 13,251, 2,687,769, 6,079,471, 6,234,236, 6,644,372, and 7,159,634 and U.S. Patent Application Publication Nos. 2007/0163727, 2004/0129390 disclose examples of such window coverings. Window coverings are typically mounted adjacent a window and are used to cover the window and provide a desired aesthetic effect to the interior and exterior of a home, office or other building. The window covering material is often moveable from a retracted position adjacent the headrail to various extended positions that lower the bottom rail and permit the window covering material to cover a window.
Various different lift systems are used to permit a user to adjust the position of the window covering material. For example, U.S. Pat. No. 6,991,020 to Cheng et al. discloses a window covering that utilizes a cord lock and an operator cord that extends through the cord lock and is attached to lift cords. The operator cord extends out of the cord lock and may be manipulated by a user to adjust the position of the window covering.
U.S. Pat. No. 6,837,294 to Cheng et al. provides a similar disclosure to U.S. Pat. No. 6,991,020 and also discloses a cordless shade that utilizes a spring motor that includes two spring motor cord spools. A spring motor cord is entrained about these spools and is attached to lift cords. A user adjusts the position of the window covering material by providing a downward force to the bottom rail of the window covering to extend the window covering material or an upward force to the bottom rail to permit the spring motor to retract the lift cords and the window covering material.
Cheng et al. teach that the attachment of the spring motor cord or operator cord to the lift cords should not pass over any pulley to avoid entanglement of the cords that may cause “hang up” problems that may make moving the window covering material problematic for a user. (See e.g. U.S. Pat. No. 6,991,020, Col. 3, lines 46-55). Such binding may result in a user having to exert a substantial force to extend the window covering material. Sometimes, such forces can cause the attachment between the cords to break or cause other damage to the window covering. These “hang up” problems can also result in a non-level window covering due to the entanglement of the cords, which often produces an undesirable aesthetic effect.
Further, the need for the attachment of the cords in the lift systems disclosed by Cheng et al. to not pass over a pulley limits the extent to which the window covering material may be extended below the headrail to, at most, the length of the headrail. If the full length of the headrail is filled with cords, spools and spring motor to provide a maximum length of the window covering, the window covering cannot be used in stock window covering programs or cut down programs. In these programs, window coverings are made in a limited number of stock sizes, which may then be cut down by a retailer to fit a specific window opening dimension provided by a customer. Cut down programs typically offer blinds or shades for lower prices relative to custom made window coverings because a retailer is able to take advantage of economies of scale involved in the production of the limited number of available stock sized window coverings. Window coverings that can only provide a length of extended window covering material that is relatively equivalent to the length of a headrail typically cannot provide the window covering material length necessary for use in one or more stock blinds of window covering cut down programs.
U.S. Patent Application No. 2004/0129390 to Toti discloses a window covering that includes lift cords connected to a spring motor by various interlocking gears or other transmission systems. Such interlocking gears or transmission systems can be expensive to manufacture. Moreover, such lift systems often require precise fabrication due to the need for the various interlocking components to reliably interact with each other. Often, only very large window coverings, which are typically much heavier and costlier than other window coverings, may economically include such systems and still be produced efficiently enough to meet the price expectations of a customer.
A window covering is needed that includes a connection between one or more lift cords and one or more operator cords or spring motor cords that reduces, if not completely eliminates, cord entanglement problems or “hang up” problems so that the connection of the cords may reliably pass over one or more pulleys in a window covering lift system. Preferably, such a connection does not require interlocking gears or other expensive or complicated mechanisms to provide a cost effective solution to such cord entanglement or “hang up” problems.